A 58-year-old man was admitted to the hospital for a heart failure (HF) exacerbation with suspected community-acquired pneumonia (CAP). He had a medical history of HF (left ventricular ejection fraction, 25-35%), hypertension, and type-2 diabetes mellitus.

During hospitalization, renal insufficiency was noted with a serum creatinine concentration of 1.5 mg/dL.

What other diagnostic tests would you suggest for this patient?